Yeast killer factor is a valuable phenotype used in industrial, medical, and research applications. It controls commercial fermentations, aids in identifying pathogenic biotypes, and is the active components of a topical treatment for yeast infections. It may eventually be used in the production of anti-idiotypes and of bioengineered proteins. Natural killer factor toxins vary and this variation has increased their usefulness. However, little is known about the genetic basis of killer toxin production in many killer systems. This project will increase our knowledge of natural phenotypic variation and of the genetics of killer toxin formation. To accomplish these goals, the investigator will identify and define killer phenotypes from killer Pichia collected from naturally occurring necrotic cactus tissues. The genus is composed of well defined species groups, many of which contain killer strains, Killer phenotypes will be identified by screening each killer isolate for its ability to kill a set of 70 other yeast. Physical optima will be determined for each toxin variation identified. From this database, the genetics of killer toxin production will be investigated by mating strains with different phenotypes within each group of related Pichia. Students will learn to identify yeast, to do genetic analyses, and to organize and present their data. The interdisciplinary aspects of the project will integrate concepts presented in different courses and aid in developing both quantitative and writing skills. The interdisciplinary approach will widen the students' perspectives on biology and, consequently, encourage them to widen their perspectives on choosing a career in biology.